Dental CariesChapter 13

The mouth is the gateway to the rest of the body, a mirror of our overall well-being.

Harold C. Slavkin, D.D.S. Former Director of the National Institute of Dental and Craniofacial Research, and Dean of the University of Southern California School of Dentistry

Everyday in the United States, millions of people including children, working families, and the elderly live in constant pain as a result of oral disease or injury to the mouth.

IntroductionDental caries is an infectious bacterial disease that has plagued humans since the beginning of recorded history. What is dental caries? Simply stated, it is tooth decay. Today, because of scientific advances and new technologies, dentistry is developing new strategies for managing dental caries. These strategies emphasize prevention and early intervention.

You cannot be healthy without oral health. Oral health and general health should not be interpreted as separate entities. Oral health is a critical component of health.

Dental Caries: A Bacterial InfectionThere are two specific groups of bacteria found in the mouth that are responsible for dental caries:Mutans streptococci (Streptococcus mutans) LactobacilliThey are found in relatively large numbers in the dental plaque. The presence of lactobacilli in the mouth indicates a high sugar intake.

Transmission of Caries Causing BacteriaMutans streptococci are transmitted through saliva, most frequently the mothers, to the infant. When mothers have high counts of mutans streptococci in their mouths, the babies also have high counts of the same bacteria in their mouth.Women should be certain their own mouths are healthy.When the number of caries causing bacteria in the mouth increases, the risk for developing dental caries also increases.

Dental PlaqueDental plaque is a colorless, soft, sticky coating that adheres to the teeth.Plaque remains attached to the tooth despite movements of the tongue, water rinsing, water spray, or less than thorough brushing. Formation of plaque on a tooth concentrates millions of microorganisms on that tooth.

Fig. 13-1 Dental plaque made visible with disclosing agent

Structure of EnamelEnamel is the most highly mineralized tissue in the body.Enamel is stronger than bone. Enamel consists of microscopic crystals of hydroxapatite arranged in structural layers or rods, also known as prisms.The enamel crystals are surrounded by water.The water and protein components in the tooth are important because that is how the acids travel into the tooth and the minerals travel out and the tooth structure dissolves.

Fig. 13-2 Dental caries

The Caries ProcessFor caries to develop, three factors must occur at the same time:A susceptible tooth Diet rich in fermentable carbohydratesSpecific bacteria (regardless of other factors, caries cannot occur without bacteria)

Fig. 13-3 Dental caries (Courtesy Ivoclar, Vivadent, Amhurst, NY.)

Areas for Development of CariesPit and fissure caries occurs primarily on the occlusal surfaces and buccal and lingual grooves of posterior teeth, as well as in lingual pits of the maxillary incisors.Smooth surface caries occurs on intact enamel other than pits and fissures.Root surface caries occurs on any surface of the root.Secondary, or recurrent, caries occurs on the tooth surrounding a restoration.

Stages of Caries DevelopmentIt usually takes a period of time, from months to years, for a carious lesion to develop.It is an ongoing process, characterized by alternating periods of demineralization and remineralization. Demineralization is the dissolving of the calcium and phosphate from the hydroxyapatite crystals. Remineralization is the calcium and phosphate being redeposited in previously demineralized areas.It is possible to have the processes of demineralization and remineralization occur without any loss of tooth structure.

Stages of Caries Development-contdIncipient lesion develops in the earliest stages when caries begins to demineralize the enamel.Overt, or frank, lesion is characterized by cavitation (the development of a cavity or hole in the tooth).Rampant: The time between the onset of the incipient lesion and the development of the cavity is rapid and there are multiple lesions throughout the mouth.

Fig. 13-4 A, The earliest sign of decay is decalcification (Courtesy Dr. John Featherstone, University of California, San Francisco, School of Dentistry.)

Fig. 13-4 B, Dental caries (Courtesy Dr. Frank Hodges, Santa Rosa, CA.)

Fig. 13-4 C, Dental caries (Courtesy Dr. Frank Hodges, Santa Rosa, CA.)

Fig. 13-5 Severely decayed molar on a child

Fig. 13-6 Decay on the lingual of a maxillary lateral incisor

Root CariesRoot caries is becoming more prevalent and is a concern for the elderly population who often have gingival recession exposing the root surfaces.People are living longer and keeping their teeth longer. Older people are often taking medications known to reduce salivary flow.Carious lesions form more quickly on root surfaces than coronal caries because the cementum on the root surface is softer than enamel and dentin. Like coronal caries, root caries has periods of demineralization and remineralization.

Fig. 13-7 Root caries (Courtesy Dr. John Featherstone, University of California, San Francisco, School of Dentistry.)

Secondary, or Recurrent, CariesSecondary, or recurrent, caries starts to form in the small spaces or gaps between the tooth and the margins of a restoration.Bacteria are able to thrive in these areas. When dental restorations need to be replaced, it is because there is recurrent caries under the existing restoration. New restorative materials that are bonded to the tooth structure eliminate the gap between tooth and filling where microleakage can occur. Restorative materials that slowly release fluoride help to prevent secondary caries.

Fig. 13-8 Recurrent caries under an amalgam restoration

The Role of SalivaPhysical protection provides a cleansing effect. Thick, or viscous, saliva is less effective than a more watery saliva in clearing carbohydrates.Chemical protection contains calcium, phosphate, and fluoride. It keeps calcium there ready to be used during remineralization. It includes buffers, bicarbonate, phosphate, and small proteins that neutralize the acids after we ingest fermentable carbohydrates. Antibacterial substances in saliva work against the bacteria. If salivary function is reduced for any reason, such as from illness or medications or due to radiation therapy, the teeth are at increased risk for decay.

Diagnosis of Dental CariesDetectable explorer stickRadiographsVisualLaser caries detector

Laser Caries DetectorThe laser caries detector is used to diagnose caries and reveal bacterial activity under the enamel surface.Carious tooth structure is less dense and gives off a higher reading than non- carious tooth structure.

Fig. 13-10 Visual and radiographic appearance of seemingly intact molar

Fig. 13-11 Cross section of molar showing decay

Methods of Caries InterventionFluoride: A variety of types are available to strengthen the tooth against solubility to acid.Antibacterial therapy: Products such as chlorhexidine rinses are effective. Fermentable carbohydrates: Reduce the amount and frequency of ingestion.Salivary flow can be increased by chewing sugarless gum, for example, those with a non-sugar sweetener such as xylitol.

Fig. 13-12 Preventive measures against caries. A, Fluoride rinse. B, Chlorhexidine rinse. C, Xylitol gum.

Risk Assessment for Dental CariesIf the patients risk for developing dental caries can be determined, it is possible to prevent the caries from developing by beginning appropriate preventive treatment.Caries risk assessment tests are based on the amount of mutans streptococci and lactobacilli present in the saliva.High bacterial counts indicate a high caries risk, low counts indicate a low risk for caries. If the preventive measures are not provided, carious lesions are likely to develop.

Indication for Using a Caries Risk TestNew patients with signs of caries activityPregnant patientsPatients experiencing sudden increase in incidence of cariesIndividuals taking medications that may affect the flow of salivaXerostomic patients

Indication for Using a Caries Risk Test-contdPatients about to undergo chemotherapyPatients who consume fermentable carbohydrates frequentlyPatients suffering from diseases of the autoimmune system